Canadian Council of Independent Laboratories July 2016

Transcription

1 LS 3. METHOD 3.1 ASTM D6307, Standard Test Method for Asphalt Content of Hot-Mix Asphalt by Ignition Method, shall be followed, except as amended below... ASTM 5. Apparatus 5.1 Balance, shall conform to Specification D4753 as a class GP2 balance (0.1g sensitivity) Sample Tray(s), of appropriate size that allows the samples to be spread thinly and allows air to flow up through and around the sample particles... The sample shall be enclosed completely with screen mesh, perforated stainless steel plate, or other suitable material Catch Pan, of appropriate size to hold the sample trays so that aggregate particles and melting asphalt binder falling through the screen mesh are caught Catch Pan/Sample Tray(s) Handling Apparatus, suitable for inserting catch pan and sample tray(s) into furnace and removing hot catch pan and sample tray(s) from furnace Assorted Spatulas, Pans, Bowls, and Wire Brushes, for preparing HMA mixtures and removing aggregate from sample tray(s) and catch pan Protective Gloves, well insulated and capable of withstanding 580 C Ovens, mechanical ovens, convection or forced draft, shall be provided for drying aggregates and HMA mixtures and for preheating HMA mixtures prior to ignition testing Ignition Furnace, as described in or LS 4.3 PREPARATION OF SAMPLE Section 7. Sampling is replaced with the following: 7.1 Use a sample obtained according to approved methods... Large field samples shall be reduced to the appropriate size for testing. Two methods of reducing the field sample to the testing size are acceptable: quartering or splitting using a riffle splitter Quartering: Warm the field sample to achieve sufficient workability for quartering... A conventional oven maintained at 110 C or a microwave oven (see Note 1) may be used for this purpose... The surface upon which the sample is to be reduced should be flat, non-abrasive, non-absorptive, and of sufficient area to provide for uniform quartering... Heat lamps may be used to keep the surface warm (see Note 2)... The sample shall be mixed on the surface until uniform, then quartered, and opposite quarters removed... This process is to be repeated until the testing size is obtained... Page 1 of 12

2 Note 1: Caution: Frequent mixing may be necessary to prevent localized overheating when using a microwave oven to heat paving mixtures. Also, the presence of metallic particles in some mixtures may render the microwave oven unsafe for the heating of these mixtures... Mixes made with polymer modified asphalt cement will have to be heated to a temperature higher than 110 C to achieve sufficient workability. The actual temperature should be the minimum required to achieve this and should be determined by trial and error... Note 2: If required, Pam or equivalent used in minimal quantities has been found suitable in preventing the sample from adhering to the surface. Motor oils must not be used for this purpose Riffle Splitter: Warm the field sample to achieve sufficient workability for splitting... A conventional oven maintained at 110 C or a microwave oven (see Note 1 above) may be used for this purpose... The mix may agglomerate if it is too cold, or stick to the splitter if too hot. A temperature range of 90 C to 110 C has been found to be generally satisfactory... Heat lamps may be used to keep the walls of the splitter box warm (see Note 2 above)... Chutes shall be cleaned after each split. The use of a putty knife or a 25 mm diameter wire brush used to clean glassware has been found suitable When testing core samples for asphalt cement content and sieve analysis, the core shall be warmed just sufficiently to enable the trimming of the curved surface to remove particles that were cut during the coring process... The depth trimmed shall be equivalent to the 'Designated Large Sieve' size for the particular mix type, except for HL 2 mix, for which the depth trimmed shall be approximately 4.75 mm... Dry the trimmed core to constant mass to remove moisture A single test portion shall be used to determine the asphalt cement content... The sample size for testing is governed by the Designated Large Sieve size of the mix (see Note 3) and shall conform to the requirements as shown in Table 1... Table 1 - Size of Test Sample Designated Large Sieve Size, MTO Sieve Designation, mm Minimum Mass of Sample, kg /16.0/ Page 2 of 12

3 Note 3: The Designated Large Sieve is a sieve size specifically designated for the following mixes for gradation testing: mm for HL mm for HL 1, HL 3, HL 3A, Dense Friction Course or Open Friction Course, Superpave 12.5, 12.5FC 1 and 12.5FC mm for Superpave mm for HL 4 Binder or Surface Course 16.0 mm for HL 8, Medium Duty Binder Course, or Heavy Duty Binder Course 19.0 mm for Superpave mm for Superpave 37.5 The gradation analysis shall be performed on the total test portion (see Section 4.7). 7.4 When splitting off a sample for determination of moisture content, a minimum sample size of 1000 g is required for all types of paving mix Determination of Moisture Content If moisture is present in a sample, it will appear as asphalt cement after ignition testing and internal furnace software calculations are completed, unless a correction is made... This is done by determining the amount of moisture in a 1000 g portion and: a) adjusting the asphalt cement content per cent after ignition testing or if the per cent moisture is known... b) adjusting the mean calibration factor before ignition testing... The first approach has the advantage that the 2 procedures can be run concurrently. Either way is acceptable... The weighing and recording of the masses for both the moisture content determination and the ignition tests must be done at the same time - immediately before testing for ignition... In either case, weigh the test portion to be used and record the mass to 0.1 g... Place the test portion for moisture determination in an oven maintained at 110 ± 5 C and dry to constant mass... Note 4: Constant mass is defined as no change in mass in excess of 0.1% or 1 g, whichever is less, for each 30 min drying period Reweigh the test portion and calculate its moisture content rounding off to the nearest 0.01% as follows:... Page 3 of 12

4 % Moisture Content, (Z) = (Ma - Md) x 100 Where: Ma = Original mass of mix, g Md = Mass of oven dry mix, g Md LS 4.1 APPARATUS ASTM Test Method A 8. Apparatus 8.1 In addition to the apparatus listed in Section 5, the following is required for Test method A... TABLE 1 Size of Sample Nominal Maximum Aggregate Size Minimum Mass of Sample, kg Standard, mm LS Section of ASTM D6307 is replaced with the following: FURNACE: Heats the sample by either the convection method or direct irradiation method... The convection type furnace shall have a minimum temperature capability of 580 C... The furnace chamber shall have an internal weighing system capable of measuring the mass of sample sizes of at least 2500 g... The furnace chamber shall be of sufficient size to accommodate sample sizes of at least 2500 g... A data collection system shall also be included so that the sample mass loss can be automatically determined to an accuracy of 0.1 g and displayed during a test... The equipment shall provide a printout of the test results... The equipment shall be capable of varying the test end point from 0.1 g to 1.0 g on a sample size of 1500 g (0.007% to 0.07% on 1500 g)... Page 4 of 12

5 After the testing end point criteria are met, the furnace shall be capable of alerting the operator and/or turning off the furnace heating elements... A system capable of reducing furnace emissions to a level meeting, or exceeding all Health and Safety and environmental standards, shall also be incorporated in the furnace... The furnace shall be vented into a hood or to the atmosphere and, when set up properly, will have no noticeable odours escaping into the laboratory... The furnace will have a fan with the capability to pull air through the furnace to expedite the test and to reduce escape of smoke into the laboratory... The furnace shall be equipped so that the door cannot be opened during the ignition test... ASTM Filters, if required, of the type specified by the furnace manufacturer... LS 4.2 CALIBRATION Section 9. Calibration of ASTM D6307 is modified as follows: ASTM 9. Calibration 9.1 The type of aggregate in the mixture may affect the results of this test method because different aggregates lose mass on ignition to varying degrees... The results also may be affected by presence of additives and modifiers in the HMA sample... Accordingly, to optimize accuracy, a calibration factor shall be established by testing 3 calibration samples for each mix type... The calibration shall performed on a prepared sample of asphalt mixture, which also shall include addictives and modifiers if any to be used Obtain samples of blended aggregate to be used in HMA in accordance with The sample should be approximately the same mass and gradation as that to be used for the HMA test sample (10.1)... LS To Clause 9.2, add: Each constituent aggregate shall be fractioned on all sieves down to the 2.36 mm sieve, with the passing 2.36 mm sieve collected as a single fraction... Prepare the calibration samples by reconstituting to the JMF gradation up to and including the 2.36 mm sieve using the proportions indicated in the mix design... The total fraction passing the 2.36 mm shall be obtained by drawing from the passing 2.36 mm of each constituent in the proportion of its source material as per the mix design... For recycled mixes, include the amount of RAP calculated on the basis of the mix design to the aggregate blend... The RAP shall be prepared in accordance with LS Page 5 of 12

6 ASTM 9.3 Obtain samples of asphalt cement to be used in HMA in accordance with Oven-dry the aggregate samples to a constant mass For the convection type furnace, set the furnace temperature to C for calibration using mixtures For the direct-irradiation type furnace, set the burn profile to the DEFAULT mode Heat the aggregates and asphalt cement to approximately 150 C. Heat all mixing bowls and tools to appropriately 150 C Prior to the mixing of the calibration samples, an initial or butter mix is required to condition the mixing equipment. Remove and discard the butter mix from the bowl by scraping, leaving a uniform coating of asphalt mix residue... Note 4 - The butter mix prevents calibration samples from being biased by residual asphalt mix retained in the mixing bowl Prepare 3 calibration samples at the design asphalt cement content (P). Incorporate additives and modifiers, if any, to be used... LS To Clause 9.7, add: If RAP is a constituent of the mix, the design asphalt content includes AC from this RAP... Allowance shall be made for this quantity of asphalt cement already in the aggregate blend by determining the AC content of the RAP through solvent extraction (Methods LS-282 or LS-291)... The gradation of the extracted RAP shall also be carried out as part of this calibration... Certain aggregate types may result in an unusually high calibration factor and erroneous gradation results due to aggregate breakdown... It is, therefore, necessary to prepare the requisite calibration samples for AC content and 2 additional blank samples for gradation calibration (to which no asphalt cement will be added and which will not be subject to burning in the furnace)... For recycled mixes, RAP shall not be incorporated in the blank (gradation calibration) samples. Once the blank samples have been prepared, carry out a washed sieve analysis of each of the blank samples and obtain the mean gradation... For mixes containing no RAP, this will be the gradation to which the gradation of the burnt calibration samples will be compared to calculate the correction factors for each sieve... For recycled mixes, the mean gradation of the blank samples will be mathematically combined with the gradation of RAP (determined after solvent extraction)... ASTM 9.8 Determine and record the mass of the sample tray(s) and catch pan to the nearest 0.1 g 9.9 Evenly distribute the sample in the sample tray(s) Determine the mass of the sample, sample tray(s) and catch pan to the nearest 0.1 g... Page 6 of 12

7 Calculate and record the initial mass of the sample (M 1 )... LS Clause 9.11 is replaced with the following: The furnace end point shall be set to 1.0 g for all sample sizes (0.2% by mass at 500 g sample size; 0.07% at 1500 g; 0.05% at 2000 g)... The test shall be deemed to be complete when the difference between measured loss for 3 consecutive 1 min intervals does not exceed 1.0 g... For a convection type furnace, the testing temperature chosen shall be the highest of 430 C, 480 C, or 540 C, providing that individual "calibration factorslab mix" are less than 1.0%... For a direct irradiation type furnace, follow the operating instructions provided by the device manufacturer; including setup of the burn profile for the type of mix being tested, providing that individual "calibration factorslab mix" are less than 1.0%... To optimize accuracy, a "mean calibration factorlab mix" must be obtained for each mix type... The "mean calibration factorlab mix" shall be the average of 3 "calibration factorslab mix" where the range for the 3 tests is less than or equal to 0.15%... If the range is greater than 0.15%, another 2 tests shall be done and, from the 5 tests, the highest and lowest results shall be discarded and the remaining 3 "calibration factorslab mix" averaged... The calibration factor is unique for a particular oven and the mix, and must be established before any quality control, acceptance, or referee testing is completed... To determine correction factors for gradation, perform a gradation analysis on each of the 3 residual aggregate samples (in accordance with Section 4.7) and obtain the average gradation resulting from the ignition process... A "calibration factorlab mix" for gradation for any sieve is the difference between the gradation of an ignition furnace test result produced using raw materials that are blended in the laboratory, in accordance with the job mix formula (JMF) requirements, and the gradation of the blank unburnt sample...,... A gradation correction factor is only applied when it is greater than or equal to 1.0% for any sieve except the 75 µm sieve... For the 75 µm sieve, the factor shall be applied if it is greater than or equal to 0.3%... ASTM 9.12 Measure and record the mass (M L ) of the sample ignition to the nearest 0.1 g. The mass can be obtained immediately upon completion of the test from the printout or display... LS Replace Clause 9.13 with the following: A "calibration factorlab mix" for asphalt cement content is the difference between an ignition furnace test result produced using raw materials that are blended in the laboratory, in accordance with the job mix formula (JMF) requirements and the asphalt content per cent required by the JMF, where: Page 7 of 12

8 calibration factorlab mix = ignition resultusing JMF %AC - %ACJMF... ASTM 9.14 Repeat steps 9.8 through 9.13 for 2 additional calibration samples. Calculate the average calibration factor (C F ) by averaging the 3 C F values Calibration of Temperature Adjustments For the convection type furnace, if the calibration factor exceeds 1.0 %, lower the test temperature to C and repeat steps 9.2 through Use the calibration factor obtained at 482 C even if it exceeds 1.0 % For the direct irradiation type furnace, the DEFAULT burn profile should be used for most materials. The operator may select burn profile OPTION 1 or OPTON 2 to optimize the burn profile The temperature or burn profile for testing HMA samples in 10.3 shall be the same temperature or burn profile selected for testing mixture calibration samples... LS 4.4 PROCEDURE Section 10. Procedure of ASTM D6307 is amended as follows: ASTM 10 Procedure 10.1 Obtain an HMA sample in accordance with Section 7... The sample mass should be approximately the same as that used for calibration (9.2) Oven dry the sample HMA sample to constant mass at a temperature of C or determine the moisture content of the samples in accordance with Test Method D1461, so that the measured mass loss can be corrected for moisture Set the furnace temperature or burn profile in accordance with Section 9... Samples can be placed in the furnace at significantly lower temperatures, since the furnace will quickly heat to the desired temperature once the sample begins to burn. The furnace temperature is likely to increase during the ignition phase of the test... LS Clause 10.3 is amended by the addition of the following: For the convection type furnace, testing temperatures shall be one of 430 ± 5 C, 480 ± 5 C, or 540 ± 5 C, as determined by Furnace Calibration (Section 4.2). For the direct irradiation type furnace, the burn profile for testing HMA samples shall be the same burn profile selected for testing mixture calibration samples (Section 4.2). ASTM 10.4 Determine and record the mass of the sample tray(s) and catch pan to the nearest 0.1 g Evenly distribute the sample in the sample tray(s) Determine the mass of the sample, sample tray(s) and catch pan to the nearest 0.1 g... Calculate and record the initial mass of the sample (M B )... Page 8 of 12

9 10.7 Heat the sample in the furnace at the specified temperature until the difference between consecutive measured mass loss does not exceed 0.01 % of the sample mass (M B ) for 3 consecutive 1 min intervals... This point shall be determined automatically by the furnace s data collection system The furnace data collection system shall measure and record automatically the aggregate mass (M A ) of the sample after ignition to the nearest 0.1 g... The mass shall be obtained immediately upon completion of tests by subtracting the mass loss measured by the furnace from the initial mass of the mix (M B ) The corrected asphalt content shall be calculated automatically by the furnace s data collection system as follows:... % AC = M B M A X C F M B Where: AC = measured asphalt content percent by mass of the oven-dry HMA sample M A = total mass of aggregate remaining after ignition M B = total mass of the HMA sample prior to ignition C F = calibration factor obtained in Section 9 and entered into the furnace s data collection system LS The following follows Clause 10.9 of ASTM D6307: The convection furnace temperature or direct irradiation furnace burn profile used for quality control, acceptance, or referee testing must be the same as that at which the "mean calibration factor lab mix" is determined After loading the test portion into the furnace and during test initiation procedures, input the testing mass into the furnace software... Also input the mean calibration factor into the furnace software as given below For dry field samples, input the "mean calibration factorlab mix" into the furnace software.. If a) of Section is used, input the "mean calibration factorlab mix" into the furnace software... If b) of Section is used, input the "mean calibration factorfield mix" into the furnace software... Where: Mean Calibration Factorfield mix = Mean Calibration Factorlab mix + % Moisture Content... Because of per cent moisture content, this "mean calibration factorfield mix" may be greater than 1.0%... LS 4.5 ASPHALT CEMENT CONTENT CALCULATION Calculate the asphalt cement content in the test portion to 2 decimal places making use of worksheets... Page 9 of 12

10 4.5.1 If the ignition furnace test sample is dry, the ignition furnace result will be the % ACcorrect If a) of Section was used, adjust the asphalt cement content for the test portion as follows: % ACcorrect = % ACby ignition - % Moisture If b) of Section was used, the ignition furnace result will be the % ACcorrect ANALYSIS OF RESIDUAL AGGREGATE Washing of Aggregate: After the mass (W3) of the test portion of dried aggregate has been determined, return the sample to the drying pan and cover the sample with water... Add a sufficient amount of wetting agent (see Note 5) to ensure a thorough separation of materials finer than 75 µm from the coarser particles... The contents of the container shall be agitated vigorously taking care not to splash out any material, and then the wash water shall be immediately decanted over the nest of 2 sieves consisting of a 1.18 mm sieve superimposed on a 75 µm sieve... The use of a hand, a metal spoon, or a spatula to stir and agitate the aggregate in the wash water has been found to be satisfactory (see Note 6)... Note 5: Wetting agents such as Calgon or Alconox may be pre-mixed with water at 50 g/l. 100 ml of this solution is then added to the first wash of each test. It has been found advantageous to allow the first wash to soak for 5 min after the addition of the wetting agent and preliminary agitation... Note 6: The agitation shall be sufficiently vigorous to completely separate the particles finer than 75 µm from the coarser particles and bring them into suspension, in order that they may be removed by decanting the wash water. Care shall be taken to avoid, as much as possible, decanting of the coarse particles of the sample. The operation shall be repeated until the wash water is clear Return all of the material retained on the nested sieves by flushing into the washed sample in the drying pan... The washed aggregate shall be dried to a constant mass at a temperature of 110 ± 5 C and the mass determined to the nearest 0.1 g (W7) (see Note 4 above) Sieve Analysis: Transfer cooled aggregate into the nest of coarse and fine sieves... Agitate on a mechanical sieve shaker... A satisfactory end point in sieving is considered to have been reached when an additional 1 min of sieving by hand fails to change the mass on any sieve by more than 1%. This is usually about 12 min On completion of the sieving operation, separate the sieves... Each sieve shall be placed within a round stainless steel bowl and shaken manually, checking to see if additional material passes through... Any additional material should be transferred to the next smaller sieve size... Page 10 of 12

11 When emptying the sieves, gently strike the rim of the inverted sieve with the wooden handle of the sieve brush... This helps to dislodge aggregate particles from the cloth... Individual particles stuck in coarser sieves may also require help. Following this, brush the bottom surface of the sieve cloth with a circular motion... In no case shall the particles be turned or manipulated through the sieve by hand... Weigh and record cumulatively (e.g. each successive size is to be added to the previous total) on the appropriate work sheet, the mass of the fraction retained on each sieve CALCULATION OF AGGREGATE FRACTIONS: Calculate the per cent passing on each sieve in the test portion as follows:... % passing on sieve x = 100 Wx 100 Where: W3 Wx = cumulative mass retained on that sieve W3 = total mass of dry aggregate If the aggregate breakdown procedure described under 4.2 CALIBRATION (which provides amendment to Clause 9.8 of ASTM) has been completed, a correction factor for each sieve must be determined by comparing the average gradation of the blank samples (which were not subjected to burning in the furnace) on that sieve to the average gradation of the burnt calibration samples TEST METHOD B (Sections 11, 12, and 13) is deleted in its entirety. 7. GENERAL NOTES 7.1 Aggregates in the pans are weighed while still warm to the touch to avoid absorption of moisture Extreme care must be exercised when transferring aggregates from 1 container to another to avoid any loss of particles Prior to using, check each sieve for the condition of the mesh, the soldered edges, and that the sieve nest is assembled as required in descending sizes All balances or load cells should be calibrated at the start of the construction season. When an operator questions the accuracy/condition of the balance, it should be recalibrated and/or inspected immediately All equipment and testing for LS-292 shall be located in one laboratory building only... Page 11 of 12

12 7.6 In northern Ontario, gneiss/migmatite aggregate was found to physically break down when burned in an ignition furnace. Aggregate gradations changed appreciably after burning, however, no aggregate loss or burnoff occurred. The larger size aggregate would crumble when squeezed by hand. Aggregate gradation corrections could not be performed since the intensity of sieving determined the extent of aggregate breakdown. Lowering the burn temperature to the minimum specified in this test method did not correct the breakdown problem. Therefore, for asphalt containing this type of aggregate, it is not possible to use the ignition oven for the determination of gradation from bituminous paving mixtures. The ignition furnace can still be used to determine the AC content... COMMENTS Page 12 of 12